Exocoetus monocirrhus

Actinopterygii: The Actinopterygii, or ray-finned fishes, constitute a class or subclass of the bony fishes. The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines ("rays"), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii. In terms of numbers, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish. (Wikipedia)

Pelagic: Any water in a sea or lake that is neither close to the bottom nor near the shore can be said to be in the pelagic zone. (Wikipedia)

Oceanodromous: Oceanodromous fish, which occur widely throughout the world’s oceans, live and migrate wholly in the sea. They differ mainly from one another by the method and extent of their migration. (Britannica)

Tropical: The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at 23° 26' 16" (or 23.4378°) N and the Tropic of Capricorn in the southern hemisphere at 23° 26' 16" (or 23.4378°) S; these latitudes correspond to the axial tilt of the Earth. (Wikipedia)

Multicuspid: The ichthyolith has multiple cusps (for teeth) or lobes (for denticles).

Long: The ichthyolith is at least three times longer than it is wide.

Cavity: The ichthyolith has a central nerve cavity. This is a base keyword included whenever an ichthyolith has a cavity, even when the cavity is further categorized with an additional keyword.

Cavity Narrow: The ichthyolith's cavity is distinctively narrow (defined as narrower than the "walls" surrounding it at its midpoint; alternately phrased, the cavity takes up less than one-third of the total width of the cross-section at its midpoint).

Fanned: The tip/end of the ichthyolith is the widest part.